Alloying process in bonding of metals



Jan. 22, 1952 R.V D. w ssssss AN 2,583,163

Patented Jan. 22, 1952 Renefl).1 .ViZassel-man,` NewX ork; mpplicatlon May 6, 1944,5'Se'rial Nf=531 483 This invention relatestoan improved/welding,

brazing or soldering method adapted for applicaition to ferrous andnon-.ferrous base'metals.

It is a Well known phenomenon' thatthe quality of weldng, brazing and similar .bonding .operations depenfls-primarily onithe vavoidanceof oxides on the heated parent or baselmetal. It has been further .observedthat certainflalloys usefi asfiller, .weldingmr brazing rods .seem to adv'here fasterandfbetter ;thanothers .to .the base or parent metal.

It is, thereforaf one ofthe .main .objectszof this.

invention to provide ;means ;for perfecting .and speeding Wel'cling" and otherbondingoperations at lower 'temperatures lthamheretofore .used :an'd for obtaining bondsof greater'strength:andwith uniform alloying effect, Vthereby;avoiding formation of oxides or otherdisadvantageous 'influences on 'the boncl.

It' is another object :of :thisinvention to vprovide means' for allowing the-'applicationiofiwelding, brazing and soldering Operations in new/.fields of the industry where .such ioperationshave been heretofore unsuccessfully tried.

v It is a further objectofrthe present invention to provide 'means for improvingiweldingandother bonding Operations,l which take intoficonsideration .particular alloys for 'ico'mpound- .materials Vhaving an unusual :high degree of f 'aifinity -fto Jthe 'base metal with which' they Will intheir liquifiedstate bind and alloy at great speed. 1.

'It is stillanotheriobje'ct of this'invention to provide means adapte'd' toicreateiatthe'boundarybetween the parent or basemetaland'the'liquified welding, brazing' or sol'dering1 material! a' new alloy v in form of a' layer or stratum of very-l small lthickness, thereby achievingiaitrue =al1oye1dweld- Still a furthei' object 'of 'this inventioni'resides in the provision of'predeterrn'ine'd ingredientsin welcling, brazing or soldering'materialpwhich ing'redients upon contact with the :parent' metal prodnce interlockingcrystals betweenithose of the parentmetal and Sof .'thef'newly` formed'V =al1oy. ther'eby'causingia =bon`d between -thei parent metal andv welding ro'dfimaterial at greater speed, lower temperature, lowerfcost an'd' of'greaterfistrength than heretofore experenced.

Yet, another object of .this 'nventions' therprovision of means forming a :seal'- and E.protection against oxidationiof the parent metal'and disinte.. gration due to: unnecessary heat application.-

":Still another .object'ofithepresentzinventiomis to provide. a f new rbonding method, :1 in `which ia '*boundary" :al1oy;s brought. aboutn'radeinp ;substantiallyffmorexby?` the filler orarodmatertlthan 1 clzim. (cl. 117-71) by the parent metal candhavmgjz'ra: lowemmelting .pointithanlsaidaparent'metal.

A still further object':ofcthis'finventlon `is'tlfie provision'. of meanst-to effectively.gatzodswarping stresses and distortionzof the parentzmetal ;during application of thenew'zbonding'methodzwhich may. be=achieved with1less 'heatiorzggasandat a minimum of time.

These and other objectsV of ther'invention-may be i'ealized from the'xensuing :description'='which disclosesisomefexamples incorporatingahe invention.

. in order to carry;thisi-inventionzinto:eifectreference is herewith 4.made :to ;the 'iaccompanying drawing,l in which i'Fig. l `is: a 'sectional Niewoffai'weld:zassembly consisting ..of 'a. 'base ;metal withra :'weld'metal'; or alloy applied.theretoeinanccordance mithtthe. in- Vention. f

``.Fig 2 is..aview-;of;a;:section':of theassemblyof 1 shownon enlargedscale.

As may. be ;realized from:;Fig.:1,base :metal'i is overlaid or surfacedby ai seam of'weld'metall I, at leastone of :the ingredients ofithezlatterpossessingr an .unusual' hi'ghiidegre :of 1 afii'nity f'tot-the base metal. ;Itiwillbe observedithatattheuncture of the base metal vSand :the ='.we1d ifmetala 'fboundary" :alloycor fistratum .1 |2 :is caused: to? be formed .which includes lproportionatelyfsaid ingredient or1-ingredients;famifzcomponent or components of Vthe base metal andzisffurthercharaciterized .by a lreduced thickness (sometimes'less than one thousanclth- (l/iuobyof'f-an' inch) and'byaaJ cast-like'fdendriticfstructural formaton.

Fig. 2 illustratesfon enlargediscale '-'boundary" alloy |2-extendingllengthwise-of'the base metal IO and having upper and lower limitsf |-3-M. IThe transition between stratum |2 'and *weld *metal layer I l' isfratherf abruptias observedV upon'- metallographic `examination,iwhereas'fzone |5 of ``the base Vmetal neighbouring said stratum vis interspei'sed-Lwith the eorementioned ingredient or'ingredientsshowing upon-microscopic' examination considerable intergrannlar penetrationli'between the weldfimetal 'an'd'base :metaL-;as' in'dicatdby numeral [6.

' lt will be noted' that"-bonbetwemwem'metal and base 'metal "thus attained Vshow :greater strength withv perfect'alloying e'ffectfthan` heretofore experienced. The welding or brazing'operation may be performed'at; great speed ani-ll at lower temperatures and such operation'mayi'be 'apple'd to different' types'obasemetals and 'in new fleldsof'the i'ridustryiwhere:successpreviously'met nnusuat dfiicu'ties.

In the course of various tests, it has been found that when certain metals or components are present in alloys to be employed as welding, brazing or soldering alloys and upon liquification thereof by means of an oXy-acetylene fiame, they will not only adhere to the preheated parent or base metal but form a new alloy at the junction or boundary between the liquid alloy and the solid parent metal whichmay be preheated far below its fusion point. This so-called "boundary alloy insures a real weld, is of crystalline form, is free of any or excessive impurities and the crystals of the newly formed alloy interlock with the crystals of the parent metal.

The Welding alloy containing entirely or partially predetermined metals or vcomponents of such metals, which should be carefully chosen. permits the obtainment of bonds of considerable strength and at relativel;7 low cost which, due to the formation of an apparently eutectic boundary alloy, forms a seal against oxidation of the parent or base metal and protects weld and base metal against disintegration through excessive heat application. Joints produced according to the invention are extremely clean and require a minimum amount of finishing.

The new boundary alloy has generally a lower melting point than the parent'l metal and is therefore more receptive of the filler or weld metal than the parent metal, the application of the weld metal to said boundary alloy or stratum taking place under less heat and lower gas consumption.

The temperature at which the liquid alloy may "attack" the parent metal may be indicated by the melting of a fiux designed for each rod of weld metal. The iluxes act very much in the manner of a catalyst and cause reduction of surface tension. prevention of oxidation and aid in fioating to the surface impurities of the alloy newly formed. The reaction thus occurring between the weld material and the base metal during the operation produces said eutectic boundary alloy immediately and below the surface of the base'metal. Because of this alloying effect. this process is definitely "Welding" although the alloys may be applied far below the fusion temperature of the base metals.

The new process may be well illustrated by a simple experiment. A sheet of copper is coated with an appropriate fiux for an aluminum low temperature" welding rod. The copper plate is preheated andl when the melting flux indicates that the flow point of the rod is reached, the for'- ward end of the rod is forced straight down onto the surface of the copper plate. If the copper plate is held at this temperature for just a few seconds, the aluminum alloy rod will cause a sharp perforation right through the copper plate. Adjacent the perforation a eutectic alloy of copper and aluminum is formed which has a melting pointsome 700 F. below the melting point of copper. This alloy being completely molten at this temperature has allowed the aluminum rod to be passed through the copper plate at that point, without bringing about any metallurgical change in the base metal proper.

The following examples made during research and tests. demonstrate the formation of new. completely or partially eutectic, boundary alloys attained.

1. A base metal of substantially pure aluminum of 1" x 2" and l/zf' thick was overlaid by a zinctin solder. Sufiicient amount of tin was present toassure the allpy. to fiow freely. Adherence was poor at the beginning until thebase metal was heated for sufilcient period of time, at which the zinc of the solder forms an alloy with the surface of the aluminum base. The depth of penetration of zinc into the base increases rapidly since the amount of zinc in the zinc-tin solder decreased accordingly, zinc being readily absorbed by the aluminum base. The zinc-tin solder can much easier be applied and adheres better than ordinary tin-lead or ordinary tin alloys which show no afiinity to and do not readily form an alloy with aluminum. The base metal of aluminum clearly shows a stratum or zone which is enriched by zincl due to the penetration of zinc, whereas the layer above said stratum contained only a fraction of the zinc previously included in the solder.

2. A copper-zinc base plate about 116 thick, having a melting point of about 1700 to 1800a F. and c'omprising 40% to 60% by weight of copper, was preheated to approximately 1100* F. An appropriate flux was applied to the base surface prior to its preheating. At approximately l100 F. an aluminum alloy containing approximately 10% to 15% by weight of silicon was melted down on said preheated base and it 'was noticed that a drop of said aluminum-Silicon alloy turned dark very rapidly, particularly where it came in direct contact with the surface of the base. By exerting a slight pressure on the base by means of the aluminum-Silicon rod. this alloying effect can be speeded up considerably and the base surface will disintegrate and a large hole was left at the location where said pressure occurred. The entire operation was performed at l100 F. which is far below the melting point of the base metal. A large amount of Silicon from the aluminum-Silicon alloy formed a new copper-Silicon alloy on the surface of the base, and a considerable amount of the aluminum has alloyed itself with the zinc constituent of the base metal. These new alloys have a much lower melting point than the brass of the base. It was therefore relatively easy to break the new molten alloys under slight pressure exerted by means of the welding rod.

3. A base metal in form of a copper sheet was welded by means of a rod containing about to by weight of copper and 5% to 10% by weight of phosphorus. A formation of a phosphorus-copper eutectic alloy was brought about immediately on the surface of the copper sheet. It was impossible to remove the stratum of this eutectic alloy although extremely thin, the great affinity of phosphorus to copper being noticeable because it was difcult to control the fiow of the deposited welding alloy. The afinity of phosphorus to copper is so considerable that the oxides on copper were broken up and no flux Was necessary to bring about the alloying effect.

4. A wrought iron slug of 1" x 2 and 1/2" thick was heated up to about 1800" F. by means of .an oxy-acetylene with or without application of flux. The flame was regulated to provide an excess of acetylene whereby the carbon supply could be increased. A steel welding rod containing a somewhat higher amount of carbon vthan usual was employed as a filler metal having a melting point of over 2000 F. However, it has been found that this steel alloy need only be heated to a temperature of 2000 F. to form a eutectic alloy at the surface of the steel containing approximately 4.13% of carbon. The alloy thus brought about has a lower melting point than the base and a lower melting point than thev filler rod itself. The carbon content being aos'aiea increased by the excess of carbon from the welding flame was enhanced at the surface of the base and a glossy and easily visible new alloy was formed immediately on the base surface to which alloy the steel filler rod adhered firmly. Microscopical examination has shown that a complete bond was achieved, although the wrought ironbase has not been heated up to its fusion point, the heating temperature being only between 1742,F. and 2282 F.

It is well apparent from the aforesaid disclosure that according to this invention the base metal surface may be so prepared that the same takes in or absorbs one or more ingredients externally supplied thereto and having a high degree of aflinity to the base metal whereby an alloy stratum is attained which readily and strongly bonds itself to the base metal and has simultaneously the property of permitting adherence of the weld or bond metal with said alloy stratum. The ingredient or ingredients heretofore referred to may be either contained in the weld or bonding metal or may be separately supplied, such as by means of the welding fiame. It may be further possible to apply successively several weld metals having different properties and melting points to the base metal to thereby bring about a strong bond consisting of layers the sequence of which is that the lowermost layer forms a boundary alloy with the base metal because it has the strongest afiinity to the base metal while the remaining layers bond themselves readily to the said lowermost layer and the following layers, respectively.

It is always to be kept in mind that in such cases the lowermost layer will have a lower melting point than the melting point of the base metal and any of the successive layers.

Many modifications of and various embodiments and applications of the invention are possible and may be evident to those skilled in the art without departing from the spirit and scope of this invention. The disclosure and description relating to 'this application are purely illustrative and in no way limitative.

Having thus described the invention what is claimed as new and desired to be secured by Letters Patent, is:

A welding or like bonding process in which a base metal is to be surfaced with a weld metal which process consists in supplying first a relatively thin layer of a bonding metal to the surface of said base metal and allowing under application of heat below the melting point of the base metal at least one ingredient of said bonding metal to alloy itself with at least one constituent of said base metal to which said ingredient has a high degree of affinity, providing thereby an intermediate alloy stratum having a melting point below the melting point of said base metal and that of said bonding metal, then melting' onto said alloy stratum a weld metal to thereby bond said weld metal to said base metal with said alloy stratum positioned therebetween. and thereafter applying to the layer of weld metal another layer of a different weld metal having a higher melting point.

RENE D. WASSERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 549,610 Ramage Nov. 12, 1895 1.233.803 Overend July 17, 1917 1,619,852 Conti Mar. 8, 1927 1551,709 Jones Dec. 6, 1927 1,875,911 Andrews Sept. 6, 1932 1,939,467 Short et al. Dec. 12, 1933 1,996,657 Shannon Apr. 2, 1935 2.043,952 Ffield June 9, 1936 2,055,360 Ogden Sept. 22. 1936 2.075.810 George Apr. 6, 1937 2.137,097 Sateren Nov. 15, 1938 2.147.367 George Feb. 14, 1939 2,190,267 Light Feb. 13, 1940 2,200,742 Hardy May 14, 1940 2.232.176 Guthrie Feb. 18, 1941 2,241,563 Wall May 13, 1941 2,310,568 Atlee et al. Feb. v9, 1943 2.313.315 Bla-is Mar. 9, 1943 2,330,062 Lempert Sept. 21, 1943 FOREIGN PATEN'I'S Number Country Date 13,689 Great Britain 1907 539,337 Great Britain Sept. 5, 1941 OTHER REFERENCES Eutectic Low Temp. Welding Process." pp. 2. 6, 7, 9, 10, 11, 14, 16, 17 and 25. Pub. Eutectic Welding Alloys Co., N. Y. Copyright 1942. Division 14.

The Welding Encyclopedia." 8th ed., 1932, p. 44, C01. 1. Pub. the Weld. Eng. Pub. Co., Chicago, Ill. Div. 14. 

